1. Field
The following description relates to an optical transmission technique, and more particularly, to a reflective semiconductor optical amplifier (RSOA) control technique in a RSOA-based loop-back wavelength division multiplexing-passive optical network (WDM-PON).
2. Description of the Related Art
A WDM-PON is a next generation optical network technology using WDM that overcomes the drawbacks of extension and security of an Ethernet PON (EPON) and provides a high-capacity high-quality service.
However, the WDM-PON poses an economic burden to subscribers since it needs as many specific light sources as the number of subscribers. In order to resolve this problem, a WDM-PON in which a reflective semiconductor optical amplifier (RSOA) is used as a light source using a loop-back method has been suggested.
In a RSOA-based loop-back WDM-PON, an independent light source is not provided to a subscriber, but a downlink signal transmitted from a central office (CO) is modulated or re-modulated through a RSOA, and the modulated or re-modulated signal is transmitted to the CO. Since a signal which is transmitted from the CO to the subscriber side has an individual wavelength, a distributed feedback-laser diode (DFB-LD) or a broadband light source (BLS) may be used as an independent light source.
In order to resolve a price burden and an equipment maintenance problem, a WDM-PON is being evolved into a RSOA-based loop-back WDM-PON in which a RSOA of a seed-light-injection method is used so that optical wavelengths need not be divided into individual wavelengths at the CO side.